Stero Microscopes - CMO versus Greenough

Greenough is more common. Here you have two objectives and two independent optical systems.

CMO is the other. Here "CMO" stands for Common Main Objective. Here there is one large objective which forms an image which is viewed by two eyepieces.

CMO is only found on truly high end stereo microscopes. The main advantage seems to be that it makes it easier to add accessories such as camera ports.

Low end "cheap" stereo microscopes are always Greenough, but there are some high end designs that are Greenough. It is all about the quality and the corrections designed into the components. It is generally easier (and cheaper) to produce small high quality optical components,

In the end, a CMO design is more of a "symptom" of a high quality design than a cause. A high quality Greenough scope can be very good.

• Quality and stereo microscopes